Dopamine Monoamine oxidase inhibitors

Monoamine Oxidase Inhibitors. MAOIs inactivate the enzyme MAO, which is responsible for the oxidative deamination of a variety of endogenous and exogenous substances. Among the endogenous substances are the neurotransmitters, norepinephrine, dopamine, and serotonin. The prototype MAOI is iproniazid [54-92-2] (25), originally tested as an antitubercular dmg and a close chemical relative of the effective antitubercular, isoniazid [54-85-3] (26). Tubercular patients exhibited mood elevation, although no reHef of their tuberculosis, following chronic administration of iproniazid. In... 

MAOI, monoamine oxidase inhibitor NaSSA, noradrenergic and specific serotonergic antidepressant NDRI, norepinephrine and dopamine reuptake inhibitor SARI, serotonin antagonist and reuptake inhibitor SNRI, serotonin and norepinephrine reuptake inhibitor SSRI, selective serotonin reuptake inhibitor TCA, tricyclic antidepressant. 

Synergy of unwanted pharmacological effect ginseng and its products will inhibit the central nervous system (CNS) when they are applied with luminal, chloral hydrate, or ephedrine, which can increase the release of dopamine, noradrenaline, and serotonin in the CNS thus inducing a hypertensive crisis if monoamine oxidase inhibitors (MAOIs) are given simultaneously. 

MAOI (Monoamine Oxidase Inhibitors) will intensify and prolong the effects of NN-DMT, however this is never recommended. Foolish combinations of MAOIs and other drugs can lead to serious health problems and even death. The tryptamines are normally metabolized by an MAO in the body. MAO metabolizes serotonin, norepinephrine, and dopamine. By inhibiting this, MAOIs increase levels of those neurotransmitters. Tyramine will not be metabolized and will cause an increase in tyramine levels in blood. 

DA, dopamine 5-HT, serotonin LSD, lysergic acid diethylamide, MAOI, monoamine oxidase inhibitor, NE, norepinephrine PCP,... 

DA, dopamine GABA, y-aminobutyric acid 5-HT, serotonin MAOI, monoamine oxidase inhibitor NE, norepinephrine. 

Listing of antidepressants grouped by principal mechanism of action in the synapse. Abbreviations MAOI—irreversible = irreversible monoamine oxidase inhibitor MAOI—reversible = reversible monoamine oxidase inhibitor NDRl = norepinephrine/ dopamine reuptake inhibitor NRI = norepinephrine reuptake inhibitor NSRl = norepinephrine/serotonin reuptake inhibitor NSSA = norepinephrine/specific serotonin agonist SRI = serotonin reuptake inhibitor SRl/serotonin-2 blocker = serotonin reuptake inhibitor and serotonin-2 receptor antagonist. 

Monoamine Oxidase Inhibitors (MAOIs). The MAOls work in a unique fashion by blocking the activity of an enzyme that degrades each of three key brain transmitters norepinephrine, dopamine, and serotonin. These widespread effects on several brain transmitter systems make the MAOls a potentially very effective class of medications for a variety of disorders. A few small studies have evaluated the usefulness of the MAOls in the treatment of BPD and found them moderately helpful for the impulsivity associated with this illness. Unfortunately, the requirements for strict dietary restrictions due to a risk of hypertensive crisis severely limit the usefulness of MAOls in the treatment of BPD. These restrictions are a particular concern when treating patients who have problems with impulsivity and are therefore likely to have difficulty maintaining the dietary regimen. For this reason, although they may theoretically be helpful, MAOls should only be used to treat BPD after other more easily tolerated medications have been tried and have failed. In the near future, so-called reversible MAOls that appear to avoid the need for diet restrictions may become available. If so, this will allow us to reconsider their use in the treatment of BPD. For more information regarding the use of MAOls, please refer to Chapter 3. 

A third way of promoting norepinephrine activity is to interfere with the enzyme that inactivates norepinephrine, monoamine oxidase (MAO). The monoamine oxidase inhibitors (MAOIs) work in this way. Incidentally, inhibiting monoamine oxidase also increases serotonin and dopamine activity. 

A host of medications have been nsed to treat TD including medications that block norepinephrine activity (clonidine and propranolol), dopamine-activating medications (bromocriptine), benzodiazepines, acetylcholine-activating medications, calcium channel blockers, and monoamine oxidase inhibitors. In addition, vitamin E supplementation and atypical antipsychotics including clozapine have been used to treat TD. 

Bromocriptine is a dopamine agonist acting by direct stimulation of the dopamine receptors. In Parkinson s disease, it is reserved for use in patients who are intolerant to levodopa or in whom levodopa alone is not sufficient. Orphenadrine is an antimuscarinic indicated in Parkinson s disease. Antimuscarinics tend to be more effective than levodopa in targeting tremor rather than rigidity and bradykinesia. Moclobemide is an antidepressant referred to as a reversible monoamine oxidase inhibitor (RIAAA) type A. 

Drugs that may interact with linezolid include monoamine oxidase inhibitors, SSRIs, and adrenergic agents (eg, dopamine, epinephrine). 

G.B. Baker, L.E. Hio, W.G. Dewhurst, Effects of monoamine oxidase inhibitors on release of dopamine and 5-hydroxytrypamine from rat striatum in vivo, Cell. Mol. Biol. 26 (1980) 182-186. 

Monoamine oxidase inhibitors. The monoamine oxidase inhibitors (MAOIs) inhibit the intracellular catabolic enzyme monoamine oxidase. There are two types of monoamine oxidase MAO-A and MAO-B, both of which metabolize tyramine and dopamine. In addition, MAO-A preferentially metabolizes norepinephrine, epinephrine, and serotonin, and MAO-B preferentially metabolizes phenylethylamine (an endogenous amphetamine-like substance) and N-methylhistamine (Ernst, 1996). Some MAOIs are selective for A or B and some are nonselective (mixed). In addition, irreversible MAOIs (e.g., phenelzine, tranylcypromine) are more susceptible to the cheese effect than are the reversible agents (e.g., moclobemide). 

Nolen WA, Haffmans PMJ, Bouvy PF, et al Monoamine oxidase inhibitors in resistant major depression. J Affect Disord 28 189-197, 1993 Nomikos GC, Damsma G, Wenkstern D, et al Chronic desipramine enhances amphetamine-induced increases in interstitial concentrations of dopamine in the nucleus accumbens. Eur J Pharmacol 195 63-73, 1991 Nomikos GC, Damsma D, Wenkstern D, et al Effects of chronic bupropion on interstitial concentrations of dopamine in rat nucleus accumbens and striatum. Neuropsychopharmacology 7 7-14, 1992... 

DA=dopamine XR=extended-release 5-HT2=serotonin type 2 receptor MAOIs=monoamine oxidase inhibitors MAO=... 

M. Naoi, W. Maruyama, G. M. Nagy (2004). Dopamine-derived salsolinol derivatives as endogenous monoamine oxidase inhibitors occurrence, metabolism and function in human brains. Neurvtoxicology 25 193-204. 

The enzyme MAO metabolizes some of the neurotransmitters affected by some drugs of abuse, namely epinephrine, norepinephrine, dopamine, and serotonin. Dangerously high levels can result if an inhibitor of this enzyme, or monoamine oxidase inhibitor (MAOI), is used along with the drug of abuse. 

The effect of dopamine is prolonged and intensified by monoamine oxidase inhibitors (MAOIs). If dopamine must be administered to a patient on these drugs, the dose should be reduced to one-tenth or less of that normally used. Concomitant medication with tricyclic... 

A growing number of drugs are used that affect the many neurotransmitters in the brain benzodiazepines and others act on GABAergic transmission antidepressants, such as monoamine oxidase inhibitors and tricyclic antidepressants, are thought to increase the concentration of transmitter amines in the brain and so elevate mood—these will also act at peripheral nerve terminals, so interactions with them are a combination of peripheral and central actions. Levodopa (L-dopa) increases central as well as peripheral dopamine, and the newer class of psychoactive drugs, the selective serotonin reuptake inhibitors (SSRIs) of which the ubiquitous fluoxetine (Prozac) is best known, act in a similar way on serotonergic pathways. 

The first generation of antidepressants, MAO (monoamine oxidase) inhibitors, inhibited neurotransmitter degradation by inhibiting monoamine deoxidase, a flavin containing enzyme, found in the mitochondria of neurons and other cell types, that oxidatively deaminates naturally occurring sympathomimetic monoamines, such as norepinephrine, dopamine, and serotonin within the presynapse. In 1952, isoniazid and its isopropyl derivative, iproniazid (1), were developed for the treatment of tuberculosis, where it was subsequently found that these agents had a mood enhancing effect on... 

Monoamine oxidase inhibitors MAO is found in neural and other tissues, such as the gut and liver. In the neuron, this enzyme functions as a "safety valve" to oxidatively deaminate and inacti vate any excess neurotransmitter molecules (norepinephrine, dopamine, or serotonin) that may leak out of synaptic vesicles when the neuron is at rest. The MAO inhibitors2 may irreversibly or reversibly inactivate the enzyme, permitting neurotransmitter molecules to escape degradation and, therefore, to both accumu late within the presynaptic neuron and to leak into the synaptic space. This causes activation of norepinephrine and serotonin receptors, and may be responsible for the antidepressant action of these drugs. 

Dopamine is oxidized to 3,4-dihydroxyphenylacetaldehyde by the enzyme monoamine oxidase. Inhibitors of acetylcholinesterase are widely used as insecticides inhibitors of monoamine oxidase are helpful in treating some neurological disorders. 

Monoamine oxidase inhibitors (MAOIs), which were amongst the first antidepressant drugs to be used clinically. They affect one or both of the brain monoamine oxidase enzymes that play a role in the metabolism of serotonin, noradrenaline, dopamine and adrenaline. MAOIs inhibit breakdown of the neurotransmitters important in determining mood, which results in the antidepressant effect. 

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